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Why you shouldn't worry about keeping things in focus
970 2 2016-10-12
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KLRico
lvl.2
Flight distance : 428448 ft
United States
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I see a lot of people have been concerned that they will have to continuously refocus while they're flying. I don't believe that it will be as big as a problem as it might seem, here's why:
  
  
You’ve probably noticed that when focusing an image on a camera you make your adjustments depending on the subject's distance, but there's a certain point where you don't need to adjust for focus anymore; i.e. "focused at infinity". This is the "hyperfocal distance", and is basically because at this point all the light rays coming from your subject can be considered parallel, and they can’t get “more parallel” by increasing the distance.

The hyperfocal distance is a function of focal length, aperture, and the size of the “circle of least confusion” (which is the smallest possible size of the focal point, think of that spot when you use a magnifying glass to make a fire; this spot always has a measurable diameter)
  
  
The Mavic is said to have a lens that is equivalent to 28mm, but it’s actual focal length is much smaller, because it’s scaled to the sensor size. The 1/2.3” sensor is 5.7x smaller than the standard 35mm format, so we can find that the Mavic’s true focal length is 4.91mm. We also know from the specs that the aperture is fixed at f/2.2
  
  
Punching these numbers in the calculator at http://www.outsight.com/hyperfocal.html shows that the hyperfocal point is at 6.8ft (2.07m), and the close focus point is at 3.4ft (1.03m). I think that probably covers 99% of most people's flying, so there's really nothing to worry about.
  
  
TLDR; You can focus on something that’s 7ft away and not have to touch the focus again unless you get closer than 3.4ft.  
2016-10-12
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Maverikster
lvl.3
Flight distance : 24672 ft
Netherlands
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That's very interesting. To be honest, I had no idea that hyperfocal distance could be this short. Thanks!
2016-10-12
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gt3rs
lvl.4
Flight distance : 280056 ft
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In fact I DJI should default the camera at 10 feet and have the option to switch to tap to focus for the people that needs close-up capability. It would avoid a lot of trouble to people that do not understand how focusing work....
2016-10-13
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